Merc 3.0 still chirping

[rcarden711]

Re: Merc 3.0 still chirping

Hi Fishermark,

On my end, it sounds like crickets chirping as I am revving the engine. I am not sure what engine miss sounds like. I just changed the sparkplugs today and had a tune up at beginning of this summer.

Is a compression test and a leak down test something that can be done myself?

Thanks!

 

[Fishermark]

Re: Merc 3.0 still chirping

Easy to do with the right tools.

 

[rcarden711]

Re: Merc 3.0 still chirping

Just got a compression test kit and will see what happens tomorrow. My wife keeps asking I don't take the boat to a mechanic and be done with it.

That's when I showed her this website and she simply said, "Oh."

 

[dingdongs]

Re: Merc 3.0 still chirping

make a good mix up of washing up liquid and water and brush it around head gasket and manifold to see if any leaks r visible of gas escaping. try removing belt too briefly to eliminate anything that its rotating.

 

[Alpheus]

Re: Merc 3.0 still chirping

If you can change your intake gasket, then you have enough skill o pull your outdrive if need be. Dont under estimate yourself.

Here is a video that explains how a leakdown test works. You just make sure the cylinder you are checking is on its compression stroke at TDC and introduce a measured and regulated amount of air via air compressor. (1st gauge) then the second gauge tells you the percentage of the air that is in your combustion chamber. Its nice because you can listen and find where the air is escaping to and find the leak...


http://www.youtube.com/watch?v=ofSiTGeLXvc&feature=related

 

[steddy]

Re: Merc 3.0 still chirping

One more stupid idea-
My boss had a Pontiac Grand Prix with the same exact symptoms. Turned out, the PCV valve was messed up. When the engine was running, it squealed something fierce. Turns out the PCV valve being faulty was causing air to get sucked into the crank case through the main bearing. The bearing kept being blown dry by the incoming air.
It was at the dealership for weeks while they tried to figure that one out. They even replaced that squealing main bearing 3 times in the process.

 

[rcarden711]

Re: Merc 3.0 still chirping

Just took brand new spark plugs out to do compression test and noticed all 4 plugs already had black sooty powder on them...they were not bad and they didn't have any oil on them, but they were just put in yesterday.

Is it typical for plugs to get that dirty that soon? Motor cranks right up and runs perfectly EXCEPT for the chirping.

 

[Alpheus]

Re: Merc 3.0 still chirping

One more stupid idea-
My boss had a Pontiac Grand Prix with the same exact symptoms. Turned out, the PCV valve was messed up. When the engine was running, it squealed something fierce. Turns out the PCV valve being faulty was causing air to get sucked into the crank case through the main bearing. The bearing kept being blown dry by the incoming air.
It was at the dealership for weeks while they tried to figure that one out. They even replaced that squealing main bearing 3 times in the process.

No such thing on a 3.0 marine engine...

 

[rcarden711]

Re: Merc 3.0 still chirping

Finally did a compression test...all four cylindars came in at 165 to 170 psi on a dry test. With wet test, they each were about 10 PSI higher.

Also looked more into the #1 plug wire scenario. I noticed that if I removed the #1 plug while at idle, it would squeak/chirp everytime the plug wire sparked toward the distributor cap post. No chirp would sound if the cord was too far away from the post.

 

[Alpheus]

Re: Merc 3.0 still chirping

You may have some piston slap or wrist pin slop going on...

 

[rcarden711]

Re: Merc 3.0 still chirping

Thanks Alpheus...

Would my compression be that high if I had piston slap?

What is the normal range for the compression on the 3.0? I can't find it anywhere in my manuals.

I am learning all this as I go....Thanks again for your help.

 

[Alpheus]

Re: Merc 3.0 still chirping

Yes your compression would be fine because the rings are sealing. Piston slap is from when the skirt breaks off the bottom of the piston and it allows the piston some extra movement inside the cylinder,causing the piston to "slap".

Piston slap is not a death sentence. Many engines running perfectly strong with "the slap"

http://forums.iboats.com/showthread.php?t=439390


http://forums.iboats.com/showthread.php?t=359929

read post # 3 ^^^

 

[nitrosteve]

Re: Merc 3.0 still chirping

Just took brand new spark plugs out to do compression test and noticed all 4 plugs already had black sooty powder on them...they were not bad and they didn't have any oil on them, but they were just put in yesterday.

Is it typical for plugs to get that dirty that soon? Motor cranks right up and runs perfectly EXCEPT for the chirping.

How long had it ran for did it reach operating temp? If they have been in there for a awhile it could indicate a rich condition. That doesn't explain the chirp though.

 

[nitrosteve]

Re: Merc 3.0 still chirping

Finally did a compression test...all four cylindars came in at 165 to 170 psi on a dry test. With wet test, they each were about 10 PSI higher.

Also looked more into the #1 plug wire scenario. I noticed that if I removed the #1 plug while at idle, it would squeak/chirp everytime the plug wire sparked toward the distributor cap post. No chirp would sound if the cord was too far away from the post.

Nice compression... I have seen motors with 100 still run but not very well. Yours looks good, I think they say above 140-150 and no more than 10% variation as a general rule.

 

[rcarden711]

Re: Merc 3.0 still chirping

Only ran the boat with the new plugs for a few minutes...definitely not up to operating temp because I didn't want to worsen anything. Maybe the plugs weren't getting hot enough to burn off carbon. Just a guess though.

 

[rcarden711]

Re: Merc 3.0 still chirping

Took my manifold back off the recheck the gasket seal. Just found a hairline crack (picture attached) between the middle two exhaust ports.

Obviously, I need a new manifold, but could this also be the cause of the chirp noise I've been hearing?

 

[rcarden711]

Re: Merc 3.0 still chirping (FIXED!!!)

Re: Merc 3.0 still chirping (FIXED!!!)

Just wanted to provide an update to my 1999 3.0 Mercruiser's mysterious chirping sound in case anyone else ran into same problem.

The culprit was a rusted out head bolt on the port side of Cyl #1. I discovered it as I was checking rocker arms. As I was checking torque on head bolts, the front right one spun freely with no bite. Pulled out bolt and threads were rusted.

Blew out hole, ordered a new bolt, applied Perfect Seal, and reinstalled only to find out the block's threads were gone too. Removed head so I could repair thread with a Heli-coil and found that head gasket was blown at Cyl#1.

Replaced head gasket, Installed head, adjusted rocker arms, changed oil, and cranked her up. No noise! Runs great!

My only resource was this forum and the service manuals. THANK YOU to all who take the time to offer your expertise to help others.

 

[Bluestream]

Re: Merc 3.0 still chirping

Glad you were able to isolate the problem and repair it. I wonder how you got such high engine compression readings with a blown head gasket though???

 

[CharlieB]

Re: Merc 3.0 still chirping

Combustion pressure was the culprit, compression alone was not enough pressure to leak and cause the noise.

Seen this occur with a crack inside an exhaust port, had to replace the head.

 

[rcarden711]

Re: Merc 3.0 still chirping

Bluestream, That is a good point about the high compression readings. I did another compression test after adjusting rockers and all four cylinders were right at 150.

The old head gasket wasn't 100% blown through but almost. Probably had 1/4inch of gasket material left so maybe it was still able to seal.
I looked over the head pretty good and did not see any cracks.

CharlieB, I am new to this and I am not familiar with combustion compression...how can I test for this?

Thanks,
Robert